This invention relates to a separating arrangement.
The “bodywork stiffness” is increasingly regarded as one of the most important criteria for modern motor vehicles. It makes a decisive contribution to safety, high-quality appearance and comfort. However, the increase in the bodywork stiffness is often associated with an increase in the vehicle weight, since a number of measures are frequently associated with additional or stronger bodywork components.
German document DE 198 43 025 C1 describes the possibility of increasing the bodywork stiffness while reducing the mass using a component used as standard, a dividing wall of the fuel tank. The dividing wall is of flat configuration and is virtually parallel to a vertical transverse plane of the vehicle. Angled elements and rails, with which the separating arrangement is fastened releasably to the bodywork, are in turn fastened to the dividing wall. In addition, the separating arrangement has cross-shaped cross-struts which are fitted on the separating arrangement or are integrated as a U-profile in the component.
U.S. Pat. No. 5,195,780 describes an approximately box-shaped arrangement which surrounds the fuel tank and is connected to the bodywork, this arrangement likewise contributing to stiffening the bodywork.
German document DE 196 42 820 A1 discloses a rear end of a vehicle, in particular for a convertible, which is configured in such a manner that the forces which are introduced via the chassis and via a crossmember into a central force flow center point are conducted further. The forces are distributed from there into a plurality of supports which are arranged in a manner similar to a lattice-type structure. However, the arrangement is not optimized in respect of a reduction in weight.
An object of the invention is to design a separating arrangement of a motor vehicle rear compartment in such a manner that the bodywork stiffness is increased in comparison with the prior art with a simultaneous reduction in mass.
The object is achieved according to the invention.
A novel separating arrangement according to the invention is fitted releasably in the front part of a rear compartment of a motor vehicle. It serves inter alia to partition off a fuel tank compartment from the rear compartment. The separating arrangement is positioned in such a manner that it is curved in relation to a vertical transverse plane of the vehicle (SFQ) and a horizontal transverse plane of the vehicle (WFQ). The separating arrangement is preferably curved concavely in relation to these planes but, given an appropriate distribution of space between the fuel tank compartment and rear compartment, a convex curvature may also be expedient. The curvature increases the bodywork stiffness in comparison with the prior art.
A further novel feature is that the separating arrangement has increased material thickness along the calculated force flow lines. Accordingly, material may be saved outside the force flow lines, this leading to a reduction in weight while simultaneously increasing the stiffness. The force flow lines are calculated for the corresponding bodywork with reference to standard loading situations (e.g. torsion and bending of the bodywork) with the aid of the finite element method. According to the invention, the force flow line profile is applied to the separating arrangement.
In a further advantageous refinement, the separating arrangement has, at its edges, fastening surfaces which are formed approximately parallel to the vertical or horizontal transverse planes of the vehicle. This results in a greater compensation of tolerance in two directions in space during the assembly of the body shell.
The use of elongated holes in the fastening planes additionally results in a compensation of tolerance in the third direction in space.
The separating arrangement is preferably fastened directly to the vehicle bodywork by screwing. Additional elements, such as angled components and rails, may be omitted. The number of screws is reduced. This measure contributes to the reduction in weight.
A further reduction in weight can be effected by the separating arrangement being produced in a light metal casting, in particular diecasting. Diecasting is understood here to mean all types of casting in a permanent casing die at increased pressure, for example diecasting, squeeze casting, thixocasting, thixomolding, vario-casting or low-pressure chill casting. Sandcasting processes or gravity chill casting are possible, but are not always expedient because of cost.
The abovementioned casting processes make it possible to fashion the separating arrangement according to the invention from light metals and, in particular, to vary the wall thicknesses in accordance with the invention. This results in a lower component weight and in a higher bodywork stiffness. Suitable casting metals are aluminum alloy and magnesium alloy and what is referred to as AZ91.
The reduction in weight is likewise assisted by designing the wall thicknesses between the reinforcing struts to be as thin as possible, i.e. as thin as permitted by current casting technology. At the said locations, the wall thickness is approximately 1.5 mm or less. At the present time, wall thicknesses of 1.2 mm can be reliably fashioned by casting techniques.
It is particularly expedient with regard to the reduction in weight to design the regions between the reinforcing struts to be free from material. However, this requires an additional working step and possibly an additional punching tool. The expediency of this measure is calculated in an individual case by an analysis of the cost-effectiveness.
A releasable fastening of the separating arrangement permits maintenance work in a fuel tank compartment covered by the separating arrangement.